1. Field of the Invention
The present invention relates to an apparatus with which a normally-closed valve can be manually opened.
2. Description of the Related Art
Various types of stop valves having a structure in which a valve element is normally biased in an opening or closing direction by a spring force so that an associated conduit is closed or opened when the valve element is acted upon by the pressure of a working fluid against the spring force are known in the art. However, in such types of conventional stop valves, the only way to check the operational status of the stop valve is to read a gauge, e.g., a flowmeter, or a pressure gauge.
Furthermore, various types of normally-closed valves having a structure in which a valve element is normally closed by a spring force so that the associated conduit is opened when the valve element is acted upon by the pressure of a working fluid against the spring force are known in the art. In such types of conventional normally-closed valves, under conditions which disallow the valve to be supplied with any working fluid, it is difficult to open the valve in the case where the value needs to be opened. Specifically, in a normally-closed valve whose pressure for closing the valve is high (i.e., the spring force for closing the value is great), it is more difficult to open the valve when it needs to be opened under the same conditions, and moreover, it is extremely difficult to adjust and maintain the opening state (open width) of the valve.